Research On Manufacturing And Humidity Sensing Application Of MXene Based Printing Ink

As an essential environmental parameter,humidity is required to be strictly monitored in many fields such as agricultural storage,environmental monitoring,and industrial manufacturing.People have put forward higher requirements on the performance indexes of humidity sensors such as sensitivity,hysteresis,response time,long-term stability,and humidity range.Among all kinds of humidity sensing materials,two-dimensional transition metal carbonitride(MXene),has received much attention and research due to its unique physical and chemical properties.However,the low stability of MXene in humid air or water and the lack of rapid response recovery time still limit its wide application in humidity sensors.In this thesis,the doping or surface modification of MXene material is carried out by different methods to improve its humidity sensing performance,which are mainly as follows:(1)The thesis investigated the morphology and structure of Ti₃C₂T_x MXene,and the MXene material was chosen to be prepared by the minimally intensive layer delamination method after comparative experiments.The formation of a typical layered structure of MXene with fewer defects on the surface morphology was observed using scanning electron microscope and transmission electron microscope.The results of fourier transform infrared spectroscopy confirmed the presence of a large number of hydrophilic functional groups on the surface,which were suitable as sensitive materials for humidity sensors.Furthermore,high-quality flexible interdigitated electrodes were prepared by the printed addition method,and the prepared Ti₃C₂T_x MXene was assembled as a humidity sensor by drop coating on the interdigitated electrodes as sensitive material.The response/recovery time reached 11.53 s and 12.36 s,respectively.Also,the response mechanism of the Ti₃C₂T_x MXene sensor was explained by combining it with electrochemical impedance spectroscopy.(2)Sodium ascorbate-decorated MXene(SA-MXene)material with enhanced antioxidant and humidity sensing properties was synthesized and configured into a suitable screen printing ink that maintains high stability over 30 days of storage.The flexible humidity sensor with good long-term stability(>12 days)was assembled by screen-printing technology with SA-MXene ink and the performance of the SA-MXene sensor was tested.The results showed that the SA-MXene sensor showed an ultra-high response(131.4%to 97%RH),fast response/recovery time(9.38 s/12.94 s),and excellent resistance to bending(0°-180°).In addition,the sensor showed potential for applications in real-time detection systems based on humidity changes.(3)Mussel-inspired dopamine was introduced for Ti₃C₂T_x MXene surface modification to synthesize a polydopamine-coated MXene composite(PDMX).The flexible sensor(PDMX2)was assembled by drop-coating the composite onto paper-based electrodes,and the optimal operating frequency of the sensor was explored at 200 Hz.The results showed that the humidity sensor exhibited a small hysteresis(3%RH)and a fast recovery time(<2 s).The PDMX2 sensor also exhibited the flexibility to be bent multiple times(?100 times)and long-term stability(>30 days).Due to these characteristics,the device can record and monitor physiological signals in real time,further enabling its application in the direction of respiratory detection.